The overall purpose of the project is to develop and evaluate techniques for the selection of appropriate hearing aid performance characteristics for particular individuals. The studies directed toward this goal are divided into four major areas: 1) selection strategies, 2) environment and the effects of head shadow and baffle, 3) electroacoustic measurement techniques, and 4) specification of and control over frequency response at the eardrum of the individual wearer. The work on selection strategies will include a continuation of current work on the development of the paired comparison method. In addition, various closely related alternative methods will be developed and tested in the renewal period. Some of these methods are appropriate for recorded hearing and processed test signals, and some for a conceptualized "switched master hearing aid". The environmental studies will be twofold. First the acoustical characteristics of rooms will be measured to identify an appropriate environment for hearing aid selection work. Secondly, individual differences in head baffle and diffraction effects will be measured in various environments to determine if such differences are significant factors in determining the real ear gain of a hearing aid. The electroacoustic measurement technique development will be directed toward obtaining measures of performance which adequately represent the performance of hearing aids as processors of broad band signals. Another important effort in this area will be to measure distortion production by the hearing aid in a more meaningful manner. Finally, a system will be developed to provide the clinician with a knowledge of and control over frequency response at the eardrum. The system uses a simulator which replicates the effects of particular earmold modifications and provides specifications for the physical structure of the earmold required to produce a desired result in the individual ear canal.